A vacuum insulation material has been widely used as an insulation material to follow the growing energy-saving consciousness because the thermal conductivity of the vacuum insulation material can be largely reduced as compared with that of glass wool. Accordingly, the vacuum insulation material is used not only in a form of a planar shape but also in a form of a curved shape. With this trend, for example, as described in Patent Literature 1, there is a technique in which grooves or unevenness is formed on a vacuum insulation material, which facilitates bending the material into a three-dimensional shape.
As for such a conventional vacuum insulation material, an outer packing material into which a core member is inserted is clamped from top and bottom by using molds, and protrusions are formed on a vacuum insulation material in vacuum (Patent Literature 1).